Moritte of the Frost | River Kelpie | Altar of Dementia

Cards

All permanents on the battlefield (
Moritte of the Frost as a copy of
River Kelpie).

Activate
Altar of Dementia by sacrificing
Moritte of the Frost.
When
Moritte of the Frost dies, its persist ability triggers, returning it from your graveyard to the battlefield as a copy of
River Kelpie with two additional +1/+1 counters on it and a -1/-1 counter on it.
Remove one +1/+1 counter and one -1/-1 counter from
Moritte of the Frost as a state-based action.
When
Moritte of the Frost enters the battlefield, it and
River Kelpie's first ability triggers, causing you to draw two cards.
Resolve the
Altar of Dementia ability from step 1, milling target player a number of cards equal to
Moritte of the Frost's power at the time of activation.
Repeat.